The present invention is in the field of hazardous waste control and more particularly relates to remediation of contaminated earth.
Toxic substance migration in the Earth poses an increasing threat to the environment, and particularly to ground water supplies. Such toxic substance migration may originate from a number of sources, such as surface spills (e.g., oil, gasoline, pesticides, and the like), discarded chemicals (e.g., PCB's, heavy metals), nuclear accident and nuclear waste (e.g., PCB's, solvents, methane gas). The entry of such hazardous materials into the ecosystem, and particularly the aquifer system, is well known to result in serious health problems for the general populace.
In recognition of such problems, there have been increasing efforts by both private environmental protection groups and governmental agencies, which taken together with increasing governmentally imposed restrictions on the disposal and use of toxic materials, to address the problem of long term, or permanent, safe storage of hazardous wastes, and to clean up existing hazardous waste sites.
There are many prior art techniques used to contain hazardous wastes, or other contaminants, in the ground. The most effective techniques appear to be those disclosed in U.S. Pat. Nos. 4,860,544 and 4,974,425, incorporated by reference herein, assigned to the assignee of the present invention. Generally, in accordance with the latter techniques, a frozen earth barrier, or two or more of such barriers, are established about the region containing the hazardous waste in situ. Those barriers are effective to contain, and thus prevent the migration of the enclosed hazardous waste, or other contaminants.
Once the contaminants have been contained, and even in cases where there is no containment, it is important to be able to remediate the contaminated earth. In the prior art, remediation is achieved by removing the contaminated earth to a remote site where the contaminants may be separated from the earth by conventional separation techniques. The most effective and safe approach for removal of contaminated earth for subsequent remediation is disclosed in U.S. Pat. No. 5,050,386, incorporated by reference herein, assigned to the assignee of the present invention. Generally, in accordance with an approach disclosed in that patent, the contaminated earth is frozen and then the periphery of sub-regions is thawed so that the generally frozen sub-regions may be easily removed from the site, like individual ice cubes from a tray of cubes. That approach is particularly effective where the contaminants are hazardous to humans, such as earth contaminated by radioactive waste. Even as the "cubes" are removed from the earth, a mist may be applied to the frozen cubes, which on contact freezes to establish a particulate-containing ice shell about the cube. This approach is effective for safely removing contaminated earth for remotely performed remediation.
However, it is desirable to minimize the need to transport the contaminated earth from both safety standpoints and economic standpoints. The best solution would be to remediate contaminated earth in situ, either contained as by the above noted frozen earth barrier techniques, or uncontained. In that case there would be less attendant cost, and improved safety risk factors.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for remediating contaminated earth.
Another object is to provide an in situ method and apparatus for remediating contaminated earth.
Yet another object is to provide an improved contaminated earth remediation method and system that is economic and efficient to install and operate.